The Program Project consists of six individual projects with a core facility. Fourteen investigators from four departments from the University of California at Los Angeles and at Irvine and the Jet propulsion laboratory of Pasadena are contributing the the research program. We have described in this proposal research efforts designed to continue studies on the plasticity of the neuromuscular system. The models being used to probe mammalian neuromuscular plasticity are chronic, completely low thoracic spinalized cats with and without exercise, spinalization plus deafferentation, horizontal spinal transection (separating dorsal and ventral funiculus, lumbar spinal cord isolation and compensatory hypertrophy (removal of synergistic muscles). A major emphasis in these studies is to identify the components of the neuromuscular system that are malleable, and to determine the factors that appear to be responsible for inducing the observed changes. A variety of experimental approaches are being incorporated. These approaches range from analyses of whole body function to subcellular disciplines; for example, detailed behavioral assessments that are tightly linked to specific neural and muscular events, biomechanics, neurophysiology, biochemistry, muscle physiology, vascular physiology and neuroanatomy. The integration and orientation of these multidisciplinary studies to mammalian neuromuscular plasticity should provide a better understanding of the potential of this system to recover functionally, to determine the plastic potential of some motor programs, and to identify some of the neural and muscular components that might be responsible for th changes in the motor output of the hindlimb neuromuscular system after selected lesions.